1. Field of the Invention
The present invention relates to the scanning method and apparatus of a station (STA) and, more particularly, to a method and an apparatus for performing active scanning by an STA.
2. Related Art
A recent Wireless LAN (WLAN) technology is basically evolving into three directions. There are Institute of Electrical and Electronic Engineers (IEEE) 802.11ac and IEEE 802.11ad as efforts to further increase the transfer rate on the extension line of the existing WLAN evolution direction. IEEE 802.11ad is a WLAN technology using a 60 GHz band. Furthermore, a wide area WLAN that utilizes a frequency band of less than 1 GHz in order to enable wider area transfer than that of the existing WLAN in distance is recently emerging. The wide-area WLAN includes IEEE 802.11af that uses a TV White Space (TVWS) band and IEEE 802.11ah that uses a 900 MHz band. A main object of the wide-area WLANs is to extend extended range Wi-Fi services as well as the smart grid and a wide-area sensor network. Furthermore, the existing WLAN Medium Access Control (MAC) technology is problematic in that an initial link setup time is very long according to circumstances. In order to solve such a problem and in order for an STA to rapidly access an AP, IEEE 802.11ai standardization is recently in progress actively.
IEEE 802.11ai is a MAC technology for handling a rapid authentication procedure in order to significantly reduce the initial setup and association time of a WLAN. Standardization activities for IEEE 802.11ai have been started as a formal task group on January, 2011. In IEEE 802.11ai, in order to enable a rapid access procedure, a discussion on the simplification of procedures in such fields AP discovery, network discovery, Time Synchronization Function (TSF) synchronization, authentication & association, and a procedure convergence with a higher layer is in progress. From among them, ideas, such as procedure convergence using the piggyback of a Dynamic Host Configuration Protocol (DHCP), the optimization of a full Extensible Authentication Protocol (EAP) using a concurrent IP, and efficient and selective Access Point (AP) scanning, are being actively discussed.